The function of such volume meters is to measure a volume flow. The measuring element thereof is driven by the liquid flow to be measured in accordance with the displacement principle of a gear motor. Pulses are produced by the teeth on moving past a tap hole. The sum of the pulses corresponds to the sum of the number of teeth travelling past the measuring point and is a measure for the volume flow to be measured.
Known volume meters or indicators operating according to the gear motor principle are preferably used for measurement purposes in the hydraulics industry. In the case of such instruments the gears are mounted in clearance-free, easily rotatable manner by a spindle inserted in the base part and in the top part. The two casing parts are sealed by an O-ring seal, which is inserted in a matching groove. The spindles are positioned by bearing bushes, which are fitted in the casing parts. The precise positioning of all the components is important for a high measuring accuracy of the instrument. The sensing of the speed is brought about by electronic sensors operating in contact-free manner and which art fitted to the outer circumference of the gears. The fixing of the electronic or optical pick-ups or taps usually takes place by means of holes.
Volume meters are particularly suitable for measuring a volume flow of a constant medium. When measuring different media, e.g. different varnishes or paints, considerable problems are encountered on changing between individual media. Known volume meters have pockets in which the media are deposited and can in part harden. The term pockets is here understood to mean the gaps and areas within the volume meter into which the medium to be measured can pass, but in which there is no continuous through-flow. On changing the measurement medium, such as is frequently the case in varnishing and painting installations, the residues present can contaminate the new measurement medium. In order to avoid this contamination of the measurement medium, on changing medium cleaning or washing cycles are performed for cleaning the measuring cell. In the case of known volume meters these washing cycles are time and solvent-intensive.